Why all new pipes? Unless yours are severely corroded you should be able to salvage at least some of what you've got. If you can exist without the stack for a bit then I'd take it down and see what can be salvaged before spending a fortune on all new. If it's the connection for the only loo on site then a cheap camping chemi-loo that you can empty down an manhole will suffice for a couple of weeks, especially as I understand you're not living there yet.